Brake force distribution

ABSTRACT

Brake force distribution via a combination of mechanical braking and regenerative braking techniques is described. In an example, a brake system of a vehicle can detect a braking action and can cause a first negative force to be distributed across two or more wheel assemblies associated with the vehicle. A control system of the vehicle can send a command to at least a power system of the vehicle to cause the power system to affect a second negative force on a first wheel assembly and a positive force on a second wheel assembly to cause an uneven distribution of brake force between the first wheel assembly and the second wheel assembly. As a result, a combined net braking force is applied to the front wheels—the wheels with the most grip—and a reduced net braking force to is applied to the rear wheels to prevent rear-wheel lock-up.

RELATED APPLICATION

This Application is a continuation of, and claims priority to U.S.patent application Ser. No. 15/784,017, filed on Oct. 13, 2017, entitled“BRAKE FORCE DISTRIBUTION”, which is incorporated in its entirety byreference herein.

BACKGROUND

Brake force distribution varies an amount of force that is applied tothe brake at each wheel of a vehicle based on road conditions, speed,loading, etc. Current techniques for vehicles with hydraulicallyactuated brakes utilize differences in the static sizing of vehiclecomponents (e.g., calipers and rotors associated with a rear wheelassembly are generally smaller than calipers and rotors associated witha front wheel assembly) and pressure reducing valves that aremechanically and/or electronically controlled to facilitate brake forcedistribution. An example of mechanically controlling brake forcedistribution can include a brake proportioning valve for a rear wheelassembly that reduces the hydraulic pressure supplied to the rear brakesin comparison to the front brakes. Examples of electronicallycontrolling brake force distribution can include electronic brake forcedistribution (EBD) systems and/or electronic stability control (ESC)systems.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description is described with reference to the accompanyingfigures. In the figures, the left-most digit(s) of a reference numberidentifies the figure in which the reference number first appears. Theuse of the same reference numbers in different figures indicates similaror identical components or features.

FIG. 1 is a schematic view of an example vehicle as described herein.

FIG. 2 is a schematic diagram illustrating an example of force(s) beingapplied to wheel assemblies of a vehicle based on brake forcedistribution techniques described herein.

FIG. 3 is a block diagram illustrating an example computing architectureof a vehicle as described herein.

FIG. 4 is a flowchart illustrating an example method for implementingbrake force distribution techniques described herein.

FIG. 5 is a flowchart illustrating another example method forimplementing brake force distribution techniques described herein.

FIG. 6 is a flowchart illustrating additional details associated with anexample method for implementing brake force distribution techniquesdescribed herein.

DETAILED DESCRIPTION

Techniques described herein are directed to brake force distribution. Inat least one example, techniques described herein are directed toutilizing regenerative braking in combination with mechanical braking toapply different force(s) to different wheel assemblies of a vehicle tovary the distribution of brake forces. For the purpose of thisdiscussion, regenerative braking slows a vehicle by converting thekinetic energy association with motion of the vehicle into electricalenergy that can be used immediately or stored for future use (e.g., bycharging a battery or capacitor).

In some examples, techniques described herein are directed to brakeforce distribution in bidirectional vehicles. A bidirectional vehicle isconfigured to switch between traveling in a first direction and asecond, opposite, direction. In other words, there is no fixed “front”or “rear” of the vehicle. Rather, whichever end of the vehicle isleading at the time becomes the “front” and the trailing end becomes the“rear.” In bidirectional vehicles, the sizing of vehicle components canbe substantially the same on both wheel assemblies. That is, inbidirectional vehicles, there can be substantially symmetric hardware tofacilitate the bidirectional functionality of the vehicle. In someexamples, unidirectional vehicles can also have substantially symmetrichardware. Accordingly, techniques described herein are directed toutilizing regenerative braking techniques to apply different force(s) todifferent wheel assemblies of a vehicle to improve braking performance(e.g., to mitigate wheel lock-up and control slip). In some examples,techniques described herein can implement regenerative brakingtechniques responsive to a particular event, such as a failure of astability control system (e.g., EBD, ESC, anti-lock brake system (ABS),etc.), a determination of uneven friction surfaces, etc.

As described herein, a vehicle can be associated with various systems.For instance, a vehicle can include a power system for providing powerto enable the vehicle to move in at least a first direction via anapplication of one or more positive forces. For the purpose of thisdiscussion, a positive force is an accelerating force applied in asubstantially same direction as a vehicle is travelling. In someexamples, as described herein, the power system can be used to apply anegative force as well, e.g. using regenerative braking. For the purposeof this discussion, a negative force is a decelerating force applied ina direction that is substantially opposite to the direction that thevehicle is travelling. Additionally, the vehicle can include a brakesystem for causing one or more negative forces to be applied via one ormore wheel assemblies to cause the vehicle to decrease its acceleration.

As the name implies, a bidirectional vehicle can travel in twodirections. As a result, the braking capabilities (e.g., the size of themechanical brakes) at each corner of a bidirectional vehicle aregenerally designed to be substantially the same—as opposed tounidirectional vehicles with smaller brakes at the rear of the vehicle,as discussed above. Or, unidirectional vehicles can be designed to havesubstantially symmetrical hardware. During a failure of an ESC or ABSsystem on vehicles having substantially symmetrical hardware (e.g.,bidirectional or otherwise), therefore, it can be difficult orimpossible to apply differential braking forces to safely stop thevehicle because the brakes are substantially the same size and, withoutABS or ESC, receive substantially the same hydraulic pressure. This canresult in locking of the rear wheels and loss of control, among otherthings.

In an electric vehicle, regenerative braking can be an effective tool tosafely slow a vehicle. Modern motor controllers can closely regulate thedeceleration of the motor and provide smooth stops. Motor and batterysizing, among other things, limits the amount of regenerative brakingthat can be provided. The batteries can only take a charge from themotor at a finite rate and can only do so until the battery is fullycharged. As a result, there are times when regenerative braking isinsufficient (e.g., during emergency braking, or “panic stops”) and/orunavailable (e.g., the battery is fully charged, too cool to acceptcharge, or too hot to accept charge).

To this end, examples of the present disclosure can include techniquesfor providing blended mechanical and regenerative braking to decreasestopping distances and reduce or eliminate wheel lock. In the situationwhere the hydraulic pressure to the mechanical brakes cannot beregulated (e.g., during an ABS fault), for example, a braking force canbe applied to all four wheels by the mechanical brakes. That is, thebraking force can be distributed across all four wheels of the vehicle.At the same time, a negative regenerative braking force can be appliedto the front wheels by one or more front drive motors, while a positiveforce can be applied to the rear wheels by one or more rear drivemotors. The net result is a large, combined net braking force on thefront wheels—the wheels with the most grip—and a reduced net brakingforce to the rear wheels to prevent lock-up. In some examples, thesystem can even be used when the batteries are fully charged—whenregenerative braking would normally not be available—because energygenerated by the regenerative braking in the front of the vehicle can beoffset by using the same amount of energy (minus any losses) to generatethe positive force at the rear of the vehicle.

The disclosure is described in the context of bidirectional vehicles.However, it should be noted, that the techniques described herein arenot limited to bidirectional vehicles. In some examples, brake forcedistribution enabled by techniques described herein can also be utilizedby unidirectional vehicles. Additionally, techniques described hereinare not limited to four-wheeled vehicles, but are merely described inthe context of four-wheeled vehicles for ease of explanation. In someexamples, brake force distribution enabled by techniques describedherein can be utilized by two-wheeled vehicles, four-wheeled vehicles,or, indeed, any ground-borne vehicles (e.g., tractor-trailers, trains,etc.).

Techniques described herein provide various improvements to conventionaltechnologies. For instance, techniques described herein offer redundancyin the event of a malfunctioning stability control system. That is, inthe event a stability control system malfunctions, techniques describedherein can enable a vehicle to decelerate without wheel lock-up duringthe deceleration. This provides redundancy that has not been availablefrom previous systems, and can be done without the addition of newhardware. Furthermore, techniques described herein do not rely upon astate of a battery of a vehicle, like conventional regenerative brakingtechniques, which cannot be utilized when the battery is fully chargedor otherwise cannot receive energy. Instead, techniques described hereincan transfer energy to alternate sources (e.g., capacitor, flywheel,resistor, heating element, rear wheel assembly, etc.), making techniquesdescribed herein more available than conventional regenerative brakingtechniques.

FIG. 1 is a schematic view 100 of an example vehicle 102 employing brakeforce distribution techniques described herein. For illustrativepurposes, the vehicle 102 is a bidirectional vehicle. As describedabove, a bidirectional vehicle is configured to switch between travelingin a first direction and a second, opposite, direction. In other words,there is no fixed “front” or “rear” of the vehicle 102. Rather,whichever end of the vehicle 102 is leading at the time, relative to thedirection the vehicle 102 is travelling, becomes the “front” and thetrailing end becomes the “rear.” In FIG. 1, the front 104 of the vehicle102 is leading, in view of the direction of travel, and the rear 106 ofthe vehicle 102 is trailing.

The vehicle 102 can include at least two wheel assemblies, a front wheelassembly 108 and a rear wheel assembly 110. In some examples, eachcorner of the vehicle 102 can be associated with a wheel assembly. Eachwheel assembly can include a plurality of components. The front wheelassembly 108 is enlarged to illustrate the various components. Forinstance, the front wheel assembly 108 can include a wheel 112, whichcan be associated with a rim and tire, that can be associated with a hub114 for mounting the wheel 112 to a suspension system of the vehicle102. Additionally, the front wheel assembly 108 can also include a brakeassembly 116. The brake assembly 116 can be controlled by a brake system118. The components of the front wheel assembly 108 are shown in asimplified format for illustrative purposes and should not limited tosuch a format. The rear wheel assembly 110 can include the substantiallysame components in a similar configuration.

As described above, the vehicle 102 can have multiple systems. Forexample, the vehicle 102 can include the brake system 118. The brakesystem 118 can apply a clamping force to a brake rotor or drumassociated with a brake assembly 116 to cause the vehicle 102 todecelerate. The brake system 118 can include a main brake actuator 120,one or more brake pressure control valves 122A and 122B, one or morebrake lines 124, and the brake assembly(s) 116 (which can includecaliper(s), rotor(s), pad(s), etc.). The brake system 118 can behydraulic or electric. Additionally, the vehicle 102 can include a powersystem, which can include one or more batteries 126, one or moreelectric busses 128, and one or more drive motors 130. The power systemcan route power from one or more batteries 126 to a transmission of thevehicle 102 (not pictured) or can send power directly to drive motor(s)130 proximate the wheel assemblies (e.g., front wheel assembly 108 andrear wheel assembly 110) or at each wheel 112 to cause the vehicle 102to accelerate. In some examples, the power system can utilize individualcomponents of the power system to affect negative force(s) on individualwheel(s) 112 of the vehicle 102 (e.g., via regenerative brakingtechniques). The vehicle 102 can also include a vehicle control system132, which can send one or more commands to other system(s) of thevehicle 102, as described below. Additional details regarding these, andother, systems are described below with reference to FIG. 3.

FIG. 2 is a schematic diagram 200 illustrating an example of force(s)being applied to wheel assemblies of a vehicle based on brake forcedistribution techniques described herein. The vehicle 102, as describedabove with reference to FIG. 1, is illustrated in FIG. 2, travelling ina same direction of travel.

FIG. 2 depicts a first friction circle 202 and a second friction circle204. A friction circle (also known as a circle of forces, tractioncircle, friction ellipse, etc.) can graphically represent tractioncapacity associated with a wheel of a vehicle. As can be understood inthe context of this disclosure, a friction “circle” can be representedas an ellipse to represent frictional forces, for example, in adirection of travel (e.g., in the x-direction) and in a directionperpendicular to the direction of travel (e.g., in the y-direction).Accordingly, the friction circle (e.g., represented as an ellipse) canbe represented by a semi-major axis and a semi-minor axis. In at leastone example, friction information (e.g., that can be used to determinefriction circle(s)) can be stored on the vehicle 102 and/or otherwiseaccessible over a network. In at least one example, techniques describedherein can leverage a signal, which can be associated with a pose of avehicle 102, to determine (e.g., via a lookup) friction informationcorresponding to the surface for each of the wheels in the vehicle 102.

The first friction circle 202 can correspond to the front wheel assembly108 and the second friction circle 204 can correspond to the rear wheelassembly 110. As brake force is applied via the brake system 118 of thevehicle 102, the weight of the vehicle 102 shifts forward. Arrows 206and 208 represent the wheel assembly loads in each friction circle 202and 204, respectively. In view of the direction of travel, the wheelassembly load on the front wheel assembly 108 has a larger magnitudethan the wheel assembly load on the rear wheel assembly 110, as shown byarrow 206 being longer than arrow 208.

The radii of the friction circles can indicate the friction force(s), or“grip,” available for each wheel (e.g., a front wheel associated withthe front wheel assembly 108 and a rear wheel associated with the rearwheel assembly 110). The diameter (and thus radius) of a friction circlecan be determined based on various factors, including the design of therespective wheel, the condition of the wheel (e.g., age, wear, etc.),the road surface, the wheel assembly load on the wheel, etc. Asillustrated in FIG. 2, the radius 210 of the first friction circle 202is greater than the radius 212 of the second friction circle 204.Accordingly, the front wheel has more friction force available due tothe increased load on the front wheels caused by the aforementionedweight shift resulting from the braking.

As described above, in bidirectional vehicles (or unidirectionalvehicles that are so designed), the sizing of vehicle components can besubstantially the same for both (or all) wheel assemblies (e.g., thefront wheel assembly 108 and the rear wheel assembly 110). That is, inbidirectional vehicles, there can be hardware symmetry (at least interms of performance) to facilitate the bidirectional functionality ofthe vehicle 102. Accordingly, responsive to a braking action, in atleast one example, an equal amount of negative force can be applied atthe front wheel assembly 108 and the rear wheel assembly 110, as shownby arrows 214 and 216, which are of equal length. For the purpose ofthis discussion, a negative force can be a decelerating force applied inan opposite direction as the direction of travel. Accordingly, the brakesystem 118 described above can apply negative forces of equal magnitudeto each of the wheel assemblies (e.g., the front wheel assembly 108 andthe rear wheel assembly 110). As illustrated, the negative forceassociated with arrow 216 applied at the rear wheel assembly 110 exceedsthe bounds of the friction circle 204. In such an example, this negativeforce (e.g., associated with arrow 216) would cause wheel lock-up in therear wheel. In alternative examples, the negative forces applied at thefront wheel assembly 108 and the rear wheel assembly 110 can be unequaland in at least one example, the negative force applied to the rearwheel assembly 110 can be such that it still exceeds the bounds of thefriction circle 204.

In at least one example, techniques described herein, as describedabove, are directed to utilizing regenerative braking techniques toapply force(s) to different wheel assemblies of a bidirectional vehicleto mitigate wheel lock-up. For instance, in at least one example, thevehicle control system 132 of the vehicle 102 can send an instruction tothe brake system 118 and/or the power system to affect an additionalnegative force on the front wheel (via the front wheel assembly 108)and, to utilize at least some of the electrical energy resulting frombraking, to affect an equal, but opposite (positive) force on the rearwheel (via the rear wheel assembly 110). That is, the power system canleverage regenerative braking to add an additional negative force 218(i.e., in addition to a negative force applied by the mechanical brakes)to the front wheel and a positive force 220 to the rear wheel that isapproximately equal in magnitude to the additional negative force 218.In this manner, the braking force applied at the front wheel assembly108 via the mechanical brakes (e.g., via the brake system 118) issupplemented with regenerative braking from the drive motors 122 (e.g.,via the power system), described above, and the braking force applied atthe rear wheel assembly 110 by the mechanical brakes (e.g., via thebrake system 118) is reduced by a positive force from the drive motors122 (e.g., via the power system).

This relationship can be shown in Equations 1-3:F _(FW) =F _(MECH) +F _(REGEN)  (1)F _(RW) =F _(MECH) −F _(REGEN)  (2)F _(FW) >F _(RW)  (3)In Equations 1-3, F_(F)w is the total amount of braking force applied toa front wheel, F_(RW) is the total amount of braking force applied to arear wheel, F_(MECH) is the amount of force applied by the brake system118, and F_(REGEN) is the amount of force applied by the power system.Further, as illustrated in the example of FIG. 2, such asymmetry in theforces applied can be optimized to match the different friction circles202 and 204 of the front and rear wheels, respectively. As such, thebraking force for the vehicle 102 is optimized (e.g., maximized) tobring the vehicle 102 to a stop in the quickest time possible withoutwheel-lock up.

As a result of supplementing mechanical braking with regenerativebraking, the brake force distribution between the front wheel assembly108 and the rear wheel assembly 110 can be apportioned such that thetotal amount of braking force applied to the front wheel is greater thanthe total amount of braking force applied to the rear wheel. Arrow 222,which represents the total amount of braking force applied to the frontwheel, is longer than arrow 224, which represents the total amount ofbraking force applied to the rear wheel. Furthermore, with the positiveforce (represented by arrow 220), the magnitude of the total brakingforce (represented by arrow 224) applied at the rear wheel assembly 110can be less than or equal to the available friction force of the rearwheel. Accordingly, responsive to a braking action, the rear wheel cancontinue to roll (e.g., maintain a rotational velocity) and rear-wheellock-up can be prevented.

Although described above, and illustrated in FIG. 2, in terms ofapplying a decelerating force at one wheel and an accelerating force atthe other, other examples can be contemplated. As non-limiting examples,such an asymmetry may be created by, for instance, applying the samebraking force to both wheels while either applying a decelerating forceor an accelerating force to one of the wheels. In such examples, thesystem may still optimize the relative forces with regards to thefriction circles 202, 204.

FIG. 2 illustrates but one implementation of the techniques describedherein. In additional and/or alternative examples, regenerative brakingtechniques can be leveraged to distribute brake forces for variousreasons. For instance, in at least one example, brake forces can bedistributed to adjust for uneven friction surfaces. Furthermore, thefriction circles 202 and 204 are simplified for the ease of discussion.In some examples, additional and/or alternative forces can also beaffecting the distribution of forces in the friction circles 202 and/or204.

It should be noted that while FIG. 2 is described with respect toapplying different forces to front wheel(s) and rear wheel(s), in someexamples, techniques described herein can be utilized to vary brakeforces between left wheel(s) and right wheel(s) and/or wheels that arediagonally positioned. That is, in some examples, the power system canaffect a negative force on a wheel on a left side of the vehicle 102 andan equal, but opposite (positive) force on a wheel on a right side ofthe vehicle 102. In some examples, the left wheel and the right wheelcan be positioned on a same end of the vehicle 102 (e.g., the front orrear) or on different ends of the vehicle 102. In some examples, suchbrake force distribution can be implemented in vehicles havingmulti-wheel independent braking capabilities (e.g., having hub motors).

FIG. 3 is a block diagram illustrating an example computing architectureof a vehicle 300 as described herein. In at least one example, thevehicle 300 can be the same vehicle as the vehicle 102 described abovewith reference to FIG. 1.

The vehicle 300 can include a vehicle computing device 302, one or moresensor systems 304, one or more emitters 306, one or more communicationconnections 308, at least one direct connection 310, and one or moredrive modules 312.

The vehicle computing device 302 can include one or more processors 314and memory 316 communicatively coupled with the one or more processors314. In the illustrated example, the vehicle 300 is an autonomousvehicle, however, the vehicle 300 could be any other type of vehicle. Inthe illustrated example, the memory 316 of the vehicle computing device302 stores a localization system 318 to determine where the vehicle 300is in relation to a local and/or global map, a perception system 320 toperform object detection, segmentation, and/or classification, and aplanner system 322 to determine routes and/or trajectories to use tocontrol the vehicle 300. Additional details of localizer systems,perception systems, and planner systems that are usable can be found inU.S. patent application Ser. No. 14/932,963, filed Nov. 4, 2015,entitled “Adaptive Mapping to Navigate Autonomous Vehicle Responsive toPhysical Environment Changes,” and Ser. No. 15/632,208, filed Jun. 23,2017, entitled “Trajectory Generation and Execution Architecture,” bothof which are incorporated herein by reference. In an example where thevehicle 300 is not an autonomous vehicle, such components can be omittedfrom the vehicle 300.

In at least one example, the vehicle computing device 302 can includeone or more system controllers 324, which can be configured to controlsteering, propulsion, braking, safety, emitters, communication, andother systems of the vehicle 300. These system controller(s) 324 cancommunicate with and/or control corresponding systems of the drivemodule(s) 312 and/or other components of the vehicle 300. In at leastone example, the vehicle control system 132 described above withreference to FIG. 1 can correspond to the system controller(s) 324.

Furthermore, the vehicle computing device 302 can include a forcedistribution module 326. The force distribution module 326 can determinewhen to apply different force(s) to different wheels (e.g., viadifferent wheel assemblies) of the vehicle 300 to vary the distributionof brake forces. In some examples, the force distribution module 326 canutilize regenerative braking techniques to affect a negative force on afirst wheel assembly and a positive force on a second wheel assembly(e.g., as described above with reference to FIG. 1). As described below,in some examples where regenerative braking techniques are employed, thepositive force can be equal to the negative force or unequal to thenegative force (e.g., in examples where some of the electrical energy isdeposited into the battery or another component). In additional and/oralternative examples, the force distribution module 326 can send aninstruction to a power system of the vehicle 300 to instruct the powersystem to affect a positive force (e.g., an accelerating force) on oneor more wheel assemblies. In some examples, a combination ofregenerative braking and acceleration techniques can be utilized by theforce distribution module 326 to affect different force(s) on differentwheels of the vehicle 300 to vary the distribution of brake forces. Inat least one example, the force distribution module 326 can distributebrake forces at any time. In additional and/or alternative examples, theforce distribution module 326 can distribute brake forces responsive todetermining an occurrence of an event.

In at least one example, the force distribution module 326 can determinean occurrence of an event. As described above, brake force distributiontechniques can be implemented responsive to a particular event, such asa braking action, failure of a stability control system, a determinationof uneven friction surfaces, etc. In some examples, the forcedistribution module 326 can receive information from one or more vehiclecomponents (e.g., a drive module controller, described below) and candetermine braking action. Responsive to receiving the indication fromthe drive module controller, the force distribution module 326 candetermine an occurrence of an event. In additional and/or alternativeexamples, the force distribution module 326 can receive information fromone or more vehicle components (e.g., a drive module controller,described below) and can determine a failure of a stability controlsystem. For instance, in such examples, a drive module controller,described below, can send an indication of a fault associated with astability control system to the force distribution module 326.Responsive to receiving the indication from the drive module controller,the force distribution module 326 can determine an occurrence of anevent.

In an additional and/or alternative example, the force distributionmodule 326 can access data associated with wheel speeds of individualwheels of the vehicle 300. Based on the data associated with the wheelspeeds, the force distribution module 326 can calculate a relative slipof each of the wheels. Leveraging the determined slip of individual ofthe wheels, the force distribution module 326 can determine variationsof friction with respect to the surface on which the vehicle 300 isdriving. That is, in some examples, a first wheel can be associated witha first wheel speed that is greater than a second wheel speed associatedwith a second wheel. In such examples, the first wheel can be on asurface having less friction (e.g., a lower friction coefficient) than asurface that the second wheel is on. Additionally and/or alternatively,individual wheels can have different wear, pressure, etc. which cancause the first wheel to be associated with the first wheel speed thatis greater than the second wheel speed associated with the second wheel.Based at least in part on determining a variation in friction withrespect to the surface on which the vehicle 300 is driving, or someother uneven distribution of friction, the force distribution module 326can determine an occurrence of an event. In at least one example, theforce distribution module 326 can refrain from determining an occurrenceof an event until a difference between two or more friction coefficientsis greater than a threshold. In such an example, responsive to thedifference in friction between two or more surfaces meeting or exceedinga threshold, the force distribution module 326 can determine anoccurrence of an event.

In some examples, the force distribution module 326 may receive a signalfrom the localization system 318 indicating a position and/ororientation of the vehicle 300. In such an example, the signal may alsocomprise, or be used to lookup, friction information corresponding tothe surface for each of the wheels in the vehicle 300 (e.g., which canbe used to determine a friction circle, etc.). Such information may beavailable from a local map stored on the vehicle 300, or otherwiseaccessible over a network. Differences in friction values may beassociated with an occurrence of an event.

Furthermore, in some examples, the force distribution module 326 canreceive an instruction (e.g., responsive to input from a computingdevice, a driver, a passenger, a remote operator, etc.) indicating anoccurrence of an event.

The force distribution module 326 can send an indication to the systemcontroller(s) 324 of the event, which can send command(s) to one or moresystem(s) of the drive module(s) 312. In at least one example, the forcedistribution module 326 can provide an indication of how force(s) are tobe distributed between different wheel assemblies of the vehicle 300 tovary the distribution of brake forces. That is, in at least one example,the force distribution module 326 can determine a magnitude and/ordirection of force to be applied at each wheel assembly of the vehicle300 and can provide an indication of such to the system controller(s)324.

In at least one example, the sensor system(s) 304 can include lightdetection and ranging (LIDAR) sensors, radio detection and ranging(RADAR) sensors, sound navigation and ranging (SONAR) sensors, locationsensors (e.g., global positioning system (GPS), compass, etc.), inertialsensors (e.g., inertial measurement units, accelerometers, gyroscopes,etc.), cameras (e.g., RGB, IR, intensity, depth, etc.), microphones,environment sensors (e.g., temperature sensors, humidity sensors, lightsensors, pressure sensors, etc.), etc. The sensor system(s) 304 caninclude multiple instances of each of these or other types of sensors.For instance, the LIDAR sensors can include individual LIDAR sensorslocated at the corners, front, back, sides, and/or top of the vehicle300. As another example, the camera sensors can include multiple camerasdisposed at various locations about the exterior and/or interior of thevehicle 300. The sensor system(s) 304 can provide input to the vehiclecomputing device 302.

The vehicle 300 can also include one or more emitters 306 for emittinglight and/or sound, as described above. The emitters 306 in this exampleinclude interior audio and visual emitters to communicate withpassengers of the vehicle 300. By way of example and not limitation,interior emitters can include speakers, lights, signs, display screens,touch screens, haptic emitters (e.g., vibration and/or force feedback),mechanical actuators (e.g., seatbelt tensioners, seat positioners,headrest positioners, etc.), and the like. The emitters 306 in thisexample also include exterior emitters. By way of example and notlimitation, the exterior emitters in this example include lights tosignal a direction of travel or other indicator of vehicle action (e.g.,indicator lights, signs, light arrays, etc.), and one or more audioemitters (e.g., speakers, speaker arrays, horns, etc.) to audiblycommunicate with pedestrians or other nearby vehicles.

The vehicle 300 can also include one or more communication connection(s)308 that enable communication between the vehicle 300 and one or moreother local or remote computing devices. For instance, the communicationconnection(s) 308 can facilitate communication with other localcomputing devices on the vehicle 300 and/or the drive module(s) 312.Also, the communication connection(s) 308 can allow the vehicle tocommunicate with other nearby computing devices (e.g., other nearbyvehicles, traffic signals, etc.). The communications connection(s) 308also enable the vehicle 300 to communicate with a remote teleoperationscomputing device or other remote services.

The communications connection(s) 308 can include physical and/or logicalinterfaces for connecting the vehicle computing device 302 to anothercomputing device or a network. For example, the communicationsconnection(s) 308 can enable Wi-Fi-based communication such as viafrequencies defined by the IEEE 802.11 standards, short range wirelessfrequencies such as Bluetooth®, or any suitable wired or wirelesscommunications protocol that enables the respective computing device tointerface with the other computing devices.

In at least one example, electrical, fluid, and/or air connections canbe provided between the drive module(s) 312 and other components of thevehicle 300. This can be accomplished via a bypass or direct connection310 in the vehicle 300 that directly connects the drive module(s) 312and other components of the vehicle. For example, if the vehicle 300includes multiple drive modules 312 and a hydraulic brake system, thehydraulic brake system of the first drive module can be in directfluidic communication with a hydraulic brake system of the second drivemodule via direct connection 310 in order to balance the pressure in thebrake systems of both drive module(s) 312. As another example,compressed air from a compressed air system of the first drive modulecan be directly connected to a compressed air system of the second drivemodule to balance air pressure of an air suspension system of one orboth drive module(s) 312. As yet another example, the direct connection310 can provide a high voltage link between the batteries of two drivemodule(s) 312 in order operate the vehicle 300 off the batteries of bothdrive module(s) 312 to maintain voltage equilibrium between thebatteries. While not shown, a switch or valve can be disposed in thedirect connection 310 in order selectively close one or more of thedirect electrical, fluid, and/or air connections between the drivemodule(s) 312.

In at least one example, the vehicle 300 can include one or more drivemodules 312. In some examples, the vehicle 300 can have a single drivemodule 312. In other examples, the vehicle 300 can have multiple drivemodules 312, which can be identical or different (e.g., one drive modulecan have a subset of the features of the other drive module, or thedrive modules can have one or more distinct or mutually exclusivevehicle systems). In an example where the multiple drive modules 312 areidentical (or substantially identical), they can provide the vehicle 300with redundancy of systems and components (e.g., sensors, battery,inverter, motor, steering, braking, suspension, stability, HVAC,lighting, drive module controller, communication connections, etc.).Thus, if a system of one drive module or a component thereof fails orneeds services, in many instances, the vehicle 300 will be able tocontinue to operate by relying on the corresponding system or componentof the other drive module. In at least one example, if the vehicle 300has multiple drive modules 312, individual drive modules 312 can bepositioned on opposite ends of the vehicle 300 (e.g., the front and therear, etc.).

In the illustrated example, the drive module(s) 312 include one or moresensor systems 328 to detect conditions of the drive module(s) 312and/or the surroundings of the vehicle 300. By way of example and notlimitation, the sensor system(s) 328 can include one or more wheelencoders (e.g., rotary encoders) to sense rotation of the wheels of thedrive modules, inertial sensors (e.g., inertial measurement units,accelerometers, gyroscopes, etc.) to measure orientation andacceleration of the drive module, cameras or other image sensors,ultrasonic sensors to acoustically detect objects in the surroundings ofthe drive module, LIDAR sensors, RADAR sensors, etc. Some sensors, suchas the wheel encoders can be unique to the drive module(s) 312. In somecases, the sensor system(s) 328 on the drive modules can overlap orsupplement corresponding systems of the vehicle 300 (e.g., sensorsystem(s) 304). For instance, when present, the LIDAR sensors on thedrive module(s) 312 can be in addition to, and can supplement the fieldsof view of, the LIDAR sensors on the vehicle 300. Other sensors such asthe inertial sensors of the drive module(s) 312 can measure the same orsimilar forces/conditions as the inertial sensors on the vehicle 300,but can measure them from the perspective of the drive module(s) 312.This can, for instance, enable to the drive module(s) 312 to operate and“balance” on their own, even when detached from the vehicle 300. In someexamples, such sensor systems 338 can include, but are not limited to,mass airflow sensors, pressure sensors for wheels, battery chargecapacity sensors, various microcontrollers capable of outputtingdiagnostic signals of associated systems or subsystems, and the like.

The drive module(s) 312 in this example include many of the vehiclesystems, including a high voltage battery 330, a motor 332 (which can bean electric drive motor) to propel the vehicle, an inverter 334 toconvert direct current from the battery into alternating current for useby other vehicle systems, a steering system 336 including a steeringmotor and steering rack (which can be electric), a brake system 338including hydraulic or electric actuators, a suspension system 340including hydraulic and/or pneumatic components, a stability controlsystem 342 for distributing brake forces to mitigate loss of tractionand maintain control, an HVAC system 344, lighting 346 (e.g., lightingsuch as head/tail lights to illuminate an exterior surrounding of thevehicle), and one or more other systems 348 (e.g., cooling system,safety systems, onboard charging system, other electrical componentssuch as a DC/DC converter, a high voltage junction, a high voltagecable, charging system, charge port, etc.). In at least one example, thebrake system 338 can correspond to the brake system 118 described abovewith reference to FIG. 1. Further, in at least one example, one or moreof the systems described can comprise a power system 350, which cancorrespond to the power system, described above with reference toFIG. 1. For instance, in at least one example, the high voltage battery330, the motor 332, etc. can be associated with the power system 350.

The drive module(s) 312 can also include a drive module controller 352to receive and preprocess data from the sensor system(s) 328 and tocontrol operation of the various vehicle systems 330-348. The drivemodule controller 352 includes one or more processors 354 and memory 356communicatively coupled with the one or more processors 354. The memory356 of the drive module(s) 312 can store a manifest 358 including a listor other data structure maintaining an inventory of the components thatare included in the respective drive module. In some examples, such aninventory can include batch numbers for various parts, components,systems, or subsystems. In some examples, the manifest 358 can begenerated and/or updated automatically by, for example, communicationwith the individual components/systems, or by sensing or reading one ormore machine readable codes associated with the individualcomponents/systems (e.g., by reading a radio frequency ID tag or barcodeapplied to each component/system). Additionally or alternatively, somecomponents/systems can be added to the manifest manually by a technicianwhen assembling or servicing the drive module(s) 312.

A diagnostics module 360 can execute on the drive module controller 352to check systems of the respective drive module(s) 312 to ensure thatthey are operating within normal operating parameters. The diagnosticsmodule 360 can employ data collected by sensor system(s) 328 of thedrive module and/or data from the sensor system(s) 304 or vehiclecomputing device 302. Any failures or anomalies can be recorded in afault log 362. The fault log 362 can include an indication of thefailure or anomalous measurement detected and an identifier of thecomponent(s)/system(s) involved. The fault log 362 can also store asnapshot of operating conditions leading up to the failure or anomalousmeasurement. The manifest 358 and the fault log 362 can be storedlocally at the drive module(s) 312 and used by service technicians totroubleshoot problems when servicing the drive module(s) 312.Additionally or alternatively, the manifest 358 and/or fault log 362 canbe reported to the vehicle computing device 302 (e.g., the forcedistribution module 326), an automated service robot, and/or to a remoteservice (e.g., a teleoperations computing device, an inventory trackingsystem, etc.). This reporting can occur periodically (e.g., daily,hourly, etc.) or upon the occurrence of certain events (e.g.,determination of a fault, detection of a collision, transit to a servicelocation, etc.). In some examples, the manifest 358 and/or fault log 362(or a subset thereof) can be included in a vehicle heartbeat signal thatis periodically transmitted to a remote fleet management system orteleoperations service.

The drive module(s) 312 also include one or more communicationconnection(s) 364 that enable communication by the respective drivemodule with one or more other local or remote computing devices. Forinstance, the communication connection(s) 364 can facilitatecommunication with other local computing devices on a respective drivemodule and/or the vehicle 300. Also, the communication connection(s) 364can allow the drive module(s) 312 to communicate with other nearbycomputing devices (e.g., detached by proximate body module, an automatedservices vehicle, a remote-control device, etc.). For instance, thecommunication connection(s) 364 can enable to the drive module(s) 312 tocommunicate with other nearby components of the vehicle 300. Thecommunication connection(s) 364 also enable the drive module(s) 312 tocommunicate with a remote teleoperations computing device or otherremote services.

The communication connection(s) 364 include physical and/or logicalinterfaces for connecting the drive module controller 352 to anothercomputing device or a network. For example, the communicationconnection(s) 364 can enable Wi-Fi-based communication such as viafrequencies defined by the IEEE 802.11 standards, short range wirelessfrequencies such as Bluetooth®, or any suitable wired or wirelesscommunications protocol that enables the respective computing device tointerface with the other computing devices.

The processor(s) 314 of the vehicle 300 and the processor(s) 354 of thedrive module(s) 312 can be any suitable processor capable of executinginstructions to process data from the sensor system(s) 304 and 328,respectively, and control operation of the vehicle systems. By way ofexample and not limitation, the processor(s) 314 and 354 can compriseone or more Central Processing Units (CPUs), Graphics Processing Units(GPUs), or any other device or portion of a device that processeselectronic data to transform that electronic data into other electronicdata that can be stored in registers and/or memory. In some examples,integrated circuits (e.g., ASICs, etc.), gate arrays (e.g., FPGAs,etc.), and other hardware devices can also be considered processors inso far as they are configured to implement encoded instructions.

Memory 316 and memory 356 are examples of non-transitorycomputer-readable media. Memory 316 and memory 356 can store anoperating system and one or more software applications, instructions,programs, and/or data to implement the methods described herein and thefunctions attributed to the various systems. In various implementations,the memory can be implemented using any suitable memory technology, suchas static random access memory (SRAM), synchronous dynamic RAM (SDRAM),nonvolatile/Flash-type memory, or any other type of memory capable ofstoring information. The architectures, systems, and individual elementsdescribed herein can include many other logical, programmatic, andphysical components, of which those shown in the accompanying figuresare merely examples that are related to the discussion herein.

FIGS. 4-6 are flowcharts showing example methods involving the use ofasymmetric braking techniques to apply force(s) to different wheelassemblies of a vehicle to vary the distribution of brake forces. Themethods illustrated in FIGS. 4-6 are described with reference to thevehicle 300 shown in FIG. 3 for convenience and ease of understanding.However, the methods illustrated in FIGS. 4-6 are not limited to beingperformed using vehicle 300 shown in FIG. 3, and can be implementedusing any of the other vehicles described in this application, as wellas vehicles other than those described herein. Moreover, the vehicle 300described herein is not limited to performing the methods illustrated inFIGS. 4-6.

FIG. 4 is a flowchart illustrating an example method 400 forimplementing brake force distribution techniques described herein.

In at least one example, a control system (e.g., system controller(s)324) can send a command to the brake system 338 and/or a power system350 of the vehicle 300. In at least one example, the force distributionmodule 326 can provide an indication of how force(s) are to bedistributed between different wheel assemblies of the vehicle 300 tovary the distribution of brake forces. That is, in at least one example,the force distribution module 326 can determine a magnitude and/ordirection of force to be applied at each wheel assembly of the vehicle300 and can provide an indication of such to the system controller(s)324.

In at least one example, the system controller(s) 324 can send thecommand directly to the power system 350. In other examples, the systemcontroller(s) 324 can send the command to the brake system 338, whichcan route the command to the power system 350. In additional and/oralternative examples, the system controller(s) 324 can send the commandto both the power system 350 and the brake system 338.

At operation 402, the brake system 338 and/or the power system 350 canaffect, during a period of deceleration, a negative force at a firstwheel assembly of a vehicle. In at least one example, the brake system338 can affect a negative force on one or more wheel assembliesresponsive to receiving the command. That is, in such an example, thenegative force can be distributed between the one or more wheelassemblies such to cause the vehicle 300 to decelerate. As such, thebrake system 402 can affect a negative force at the first wheel assemblyof the vehicle 300.

In additional and/or alternative examples, the power system 350 canaffect a negative force at the first wheel assembly of the vehicle 300.As described above, the power system 350 can route power from one ormore batteries 330 to a transmission of the vehicle 300 or can sendpower directly to motor(s) 334 proximate the wheel assemblies (e.g.,front wheel assembly 108 and rear wheel assembly 110) or at each wheelof the vehicle 300 to cause the vehicle 300 to accelerate. In someexamples, the power system 350 can utilize individual components of thepower system 350 (e.g., the motor 332, which can be run in reverse as agenerator) to affect negative force(s) on individual wheel(s) of thevehicle 300 (e.g., via regenerative braking techniques). In at least oneexample and responsive to receiving the command, the power system 350can affect a negative force on a first wheel assembly of the vehicle300.

At operation 404, the power system 350 can affect, during the period ofdeceleration, a positive force at a second wheel assembly of thevehicle. As described above, the power system 350 can route power fromone or more batteries 330 to a transmission of the vehicle 300 or cansend power directly to motor(s) 334 proximate the wheel assemblies(e.g., front wheel assembly 108 and rear wheel assembly 110) or at eachwheel of the vehicle 300 to cause the vehicle 300 to accelerate.Accordingly, in some examples, the power system 350 can affect anaccelerating force on a second wheel assembly of the vehicle 300responsive to receiving the command.

Additionally and/or alternatively, the power system 350 can affect apositive force generated from regenerative braking techniques on thesecond wheel assembly of the vehicle 300 responsive to receiving thecommand. That is, in at least one example and responsive to receivingthe command, the power system 350 can utilize at least some electricalenergy resulting from affecting the negative braking force to affect apositive force on the rear wheel (via the rear wheel assembly 110) ofthe vehicle 300.

The application of such negative and positive forces can affect anasymmetric brake force distribution during a period of deceleration,which can mitigate wheel-lock, as described above.

In at least one example, the positive force that is applied to the rearwheel by the power system 350 can be less than or equal to the negativeforce that is applied to the front wheel. In some examples, energy canbe lost in the system due to one or more transfers of energy, therebyreducing the magnitude of the positive force. In additional and/oralternative examples, as described below with respect to FIG. 5, energycan be routed to additional and/or alternative systems of the vehicle300, thereby reducing the magnitude of the positive force.

As noted above, while the first wheel assembly can correspond to a frontwheel assembly and the second wheel assembly can correspond to a rearwheel assembly, in some examples, techniques described herein can beutilized to vary brake forces between left wheel(s) and right wheel(s)and/or wheels that are diagonally positioned. That is, in some examples,the negative force can be affected on a wheel on a left side of thevehicle 300 and an equal, but opposite (positive) force can be affectedon a wheel on a right side of the vehicle 300. In some examples, theleft wheel and the right wheel can be positioned on a same end of thevehicle 300 (e.g., the front or rear) or on different ends of thevehicle 300. In some examples, such brake force distribution can beimplemented in vehicles having multi-wheel independent brakingcapabilities (e.g., having HUB motors).

FIG. 5 is a flowchart illustrating an example method 500 forimplementing brake force distribution techniques described herein.

At operation 502, a brake system 338 can determine a braking actionassociated with a vehicle 300. The vehicle 300 can include a main brakeactuator (e.g., main brake actuator 120), which can be actuated by acomputing device of the vehicle 300 (e.g., system controller(s) 324) orby a manual input (e.g., by a driver or passenger). The brake system 338can determine the braking action responsive to actuation of the mainbrake actuator.

At operation 504, the brake system 338, can apply a first negative forcewhich can be distributed between two or more wheel assemblies of thevehicle 300. Responsive to determining the brake action, the brakesystem 338 can apply a clamping force to a brake rotor or drumassociated with a brake assembly of a wheel assembly to cause thevehicle 300 to decelerate. As described above, in bidirectional vehicles(and unidirectional vehicles so designed), the sizing of vehiclecomponents can be substantially the same for both (or all) wheelassemblies. That is, in bidirectional vehicles, there can be hardwaresymmetry (at least in terms of performance) to facilitate thebidirectional functionality of the vehicle 300. Accordingly, in someexamples and responsive to a braking action, an equal amount of negativeforce can be applied at each wheel assembly. In other examples,responsive to a braking action, an unequal amount of negative force canbe applied at each wheel assembly depending on how the first negativeforce is distributed between the wheel assemblies.

The friction circles 202 and 204 are depicted next to operation 404. Asdescribed above, as brake force is applied via the brake system 338 ofthe vehicle 300, the weight of the vehicle 300 shifts forward. Arrows206 and 208 represent the wheel assembly loads in each friction circle202 and 204, respectively. In view of the direction of travel, the wheelassembly load on a front wheel assembly (e.g., front wheel assembly 108)has a larger magnitude than the wheel assembly load on a rear wheelassembly (e.g., rear wheel assembly 110), as shown by arrow 206 beinglonger than arrow 208. As described above, due to the sizing of vehiclecomponents being substantially the same for both (or all) wheelassemblies (e.g., the front wheel assembly 108 and the rear wheelassembly 110) of a bidirectional vehicle, an equal amount of negativeforce can be applied at the front wheel assembly and the rear wheelassembly, as shown by arrows 214 and 216, which are of equal length.Accordingly, the brake system 338 described above can apply negativeforces of equal magnitude to each of the wheel assemblies (e.g., thefront wheel assembly 108 and the rear wheel assembly 110).

It should be noted that while the example described above, is directedto the brake system 338 applying a brake force that can be distributedacross two or more wheel assemblies of the vehicle 300, in additionaland/or alternative examples, alternative systems can cause an unequaldistribution of brake force between the two or more wheel assemblies.For instance, the ESC, etc., when functioning properly, canintentionally apply different forces at different wheel assemblies.Furthermore, in the absence of a force distribution system, operation506, below, can be omitted, and operations 504, 508, and 510 can beperformed substantially simultaneously.

At operation 506, a force distribution module 326 can determine anoccurrence of an event (e.g., failure of a stability control system,uneven friction surfaces, etc.). As described above, the forcedistribution module 326 can determine when to apply different force(s)to different wheels (e.g., via different wheel assemblies) of thevehicle 300 to vary the distribution of brake forces. In at least oneexample, the force distribution module 326 can determine an occurrenceof an event.

In some examples, the force distribution module 326 can receiveinformation from one or more vehicle components (e.g., a drive modulecontroller 352) and can determine a failure of a stability controlsystem 342. For instance, in such examples, a drive module controller352, can send an indication of a fault associated with a stabilitycontrol system 342 to the force distribution module 326. Responsive toreceiving the indication from the drive module controller 352, the forcedistribution module 326 can determine an occurrence of an event.

In an additional and/or alternative example, the force distributionmodule 326 can access data associated with wheel speeds of individualwheels of the vehicle 300. Based on the data associated with the wheelspeeds, the force distribution module 326 can calculate a relative slipof each of the wheels. Leveraging the determined slip of individual ofthe wheels, the force distribution module 326 can determine variationsof friction with respect to the surface on which the vehicle 300 isdriving. That is, in some examples, a first wheel can be associated witha first wheel speed that is greater than a second wheel speed associatedwith a second wheel. In such examples, the first wheel can be on asurface having less friction (e.g., a lower friction coefficient) than asurface that the second wheel is on. Additionally and/or alternatively,individual wheels can have different wear, pressure, etc. which cancause the first wheel to be associated with the first wheel speed thatis greater than the second wheel speed associated with the second wheel.Based at least in part on determining a variation in friction withrespect to the surface on which the vehicle 300 is driving, or otherinconsistencies with respect to friction, the force distribution module326 can determine an occurrence of an event. In at least one example,the force distribution module 326 can refrain from determining anoccurrence of an event until a difference between two or more frictioncoefficients is greater than a threshold. In such an example, responsiveto the difference in friction between two or more surfaces meeting orexceeding a threshold, the force distribution module 326 can determinean occurrence of an event.

In some examples, the force distribution module 326 can receive aninstruction (e.g., responsive to input from a driver, passenger, remoteoperator, etc.) indicating an occurrence of an event.

While operation 506 is directed to determining an occurrence of anevent, in alternative examples, operations 508 and 510 can be performedat any time without an event taking place.

At operation 508, a control system (e.g., system controller(s) 324) cansend a command to the brake system 338 and/or a power system 350 of thevehicle 300. Based at least in part on determining an occurrence of anevent, the force distribution module 326 can send an indication of theevent to the system controller(s) 324, which can send command(s) to oneor more system(s) of the drive module(s) 312. In at least one example,the force distribution module 326 can provide an indication of howforce(s) are to be distributed between different wheel assemblies of thevehicle 300 to vary the distribution of brake forces. That is, in atleast one example, the force distribution module 326 can determine amagnitude and/or direction of force to be applied at each wheel assemblyof the vehicle 300 and can provide an indication of such to the systemcontroller(s) 324.

In at least one example, the system controller(s) 324 can send thecommand directly to the power system 350. In other examples, the systemcontroller(s) 324 can send the command to the brake system 338, whichcan route the command to the power system 350. In additional and/oralternative examples, the system controller(s) 324 can send the commandto both the power system 350 and the brake system 338.

At operation 510, the power system 350 can affect a second negativeforce on a first wheel of the vehicle 300. As described above, the powersystem 350 can route power from one or more batteries 330 to atransmission of the vehicle 300 or can send power directly to motor(s)334 proximate the wheel assemblies (e.g., front wheel assembly 108 andrear wheel assembly 110) or at each wheel of the vehicle 300 to causethe vehicle 300 to accelerate. In some examples, the power system 350can utilize individual components of the power system 350 (e.g., themotor 332, which can be run in reverse as a generator) to affectnegative force(s) on individual wheel(s) of the vehicle 300 (e.g., viaregenerative braking techniques).

In at least one example and responsive to receiving the command, thepower system 350 can affect an additional negative force on the frontwheel (via the front wheel assembly 108) of the vehicle 300. That is, inat least one example, the power system 350 can utilize regenerativebraking techniques to affect an additional negative force on the frontwheel of the vehicle 300. Accordingly, the power system 350 can leverageregenerative braking to affect an additional negative force 218 (i.e.,in addition to a negative force, represented by arrow 214, applied bythe mechanical brakes) on the front wheel, as illustrated in thefriction circle 202 that is shown next to operation 410. In someexamples, such regenerative braking force 218 may be selected tooptimize the force with respect to the friction circle associated withthe front wheel. At least a portion of energy derived from suchregenerative braking techniques may be used in operation 512, asdescribed in detail below. Furthermore, as described below, if othercomponents of the vehicle 300 are capable of receiving electric energy,some electric energy can be deposited with those components instead ofbeing used at operation 512, as described below with reference to FIG.6.

At operation 512, the power system 350 can affect a positive force on asecond wheel of the vehicle 300. In at least one example and responsiveto receiving the command, the power system 350 can utilize at least someelectrical energy resulting from affecting the negative braking force toaffect a positive force on the rear wheel (via the rear wheel assembly110) of the vehicle 300. That is, the power system 350 can leverageregenerative braking to affect a positive force 220 that isapproximately equal in magnitude to the additional negative force 218 onthe rear wheel, as illustrated in the friction circle 204 that is shownnext to operation 512.

In this manner, the braking force applied at the front wheel assembly108 via the mechanical brakes (e.g., via the brake system 328) issupplemented with regenerative braking from the power system 350, andthe braking force applied at the rear wheel assembly 110 by themechanical brakes (e.g., via the brake system 328) is reduced by apositive force from the power system 350. This relationship can be shownin Equations 1-3, above. As a result of supplementing mechanical brakingwith regenerative braking, the brake force distribution between thefront wheel assembly 108 and the rear wheel assembly 110 can beapportioned such that the total amount of braking force applied to thefront wheel is greater than the total amount of braking force applied tothe rear wheel. Accordingly, responsive to a braking action, the rearwheel can continue to roll (e.g., maintain a rotational velocity) andrear-wheel lock-up can be prevented. In some examples, such a differencebetween brake forces may be calculated to optimize braking to be withina friction circle.

In at least one example, the positive force that is applied to the rearwheel by the power system 350 can be less than or equal to the negativeforce that is applied to the front wheel. In some examples, energy canbe lost in the system due to one or more transfers of energy, therebyreducing the magnitude of the positive force. In additional and/oralternative examples, as described below with respect to FIG. 6, energycan be routed to additional and/or alternative systems of the vehicle300, thereby reducing the magnitude of the positive force. In someexamples, as described above with respect to FIG. 4, the positive force220 can be generated based on power from the poser system 350 withoutthe use of regenerative braking. That is, in some examples, operation510 can be optional. In such examples (e.g., where no regenerativebraking is used in the front wheel assembly), the positive force 220 maynonetheless be generated based on power from the power system 350 toyield a net force on the rear wheel smaller in magnitude than as appliedon the front wheel.

As noted above, while FIG. 5 is described with respect to applyingdifferent forces to front wheel(s) and rear wheel(s), in some examples,techniques described herein can be utilized to vary brake forces betweenleft wheel(s) and right wheel(s) and/or wheels that are diagonallypositioned. That is, in some examples, the power system 350 can affect anegative force on a wheel on a left side of the vehicle 300 and anequal, but opposite (positive) force on a wheel on a right side of thevehicle 300. In some examples, the left wheel and the right wheel can bepositioned on a same end of the vehicle 300 (e.g., the front or rear) oron different ends of the vehicle 300. In some examples, such brake forcedistribution can be implemented in vehicles having multi-wheelindependent braking capabilities (e.g., having HUB motors).

FIG. 6 is a flowchart illustrating additional details associated with anexample method 600 for implementing brake force distribution techniquesdescribed herein.

At operation 602, responsive to a braking action, a power system 350 canaffect a braking force on wheel assembly(s) of a vehicle 300. Asdescribed above, the vehicle 300 can include a main brake actuator(e.g., main brake actuator 120), which can be actuated by a computingdevice of the vehicle 300 (e.g., system controller(s) 324) or by amanual input (e.g., by a driver or passenger). In at least one example,a brake system 338 can determine the braking action responsive toactuation of the service brake and can send an indication of the brakingaction to the power system 350. In other examples, the systemcontroller(s) 324 can send an indication of the braking action directlyto the power system 350. In at least one example, responsive to thebraking action, the power system 350 can affect a braking force on wheelassembly(s) of the vehicle 300. In at least one example, the powersystem 350 can cause the motor 332 to run in a reverse direction tocause the vehicle 300 to slow down (e.g., to operate as regenerativebraking). As a result of the motor 332 running in the reverse direction,the power system 350 can affect a negative braking force on one or morewheels of the vehicle 300. In at least one example, the systemcontroller(s) 324 can send the indication of the braking actionresponsive to an event, as described above.

At operation 604, a power system 350 of the vehicle 300 can convert,based at least in part on the braking action, at least a portion ofkinetic energy associated with motion of the vehicle 300 into electricalenergy. In at least one example, the motor 332 can be run in reverse(e.g., as a generator) to convert kinetic energy into electrical energy.In some examples, the electrical energy generated can be routed to oneor more systems of the vehicle 300 for immediate use or storage forfuture use.

At operation 606, the power system 350 can determine whether electricalenergy can be routed to a battery 330 of the vehicle 300. In at leastone example, the power system 350 can determine whether the battery 330is capable of taking any of the electrical energy generated by thebraking force(s). In some examples, the battery 330 can be fullycharged, stressed, hot, cold, etc. such that the battery 330 cannot takeall (or, in some cases, any) of the electrical energy generated. Basedat least in part on determining that at least some electrical energy canbe routed to the battery 330 of the vehicle 300, the power system 350can route at least some electrical energy to the battery 330, as shownat operation 608. That is, based at least in part on determining thatthe battery 330 is capable of receiving at least some of the electricalenergy generated, the power system 350 can route that electrical energyto the battery 330.

In additional and/or alternative examples, the operation 608 can includerouting at least a portion of the electrical energy generated viaregenerative braking to one or more power sinks in general, and is notlimited to the battery 330. For example, at least a portion of theelectrical energy can be routed to one or more of a capacitor, flywheel,or other energy storage system.

Based at least in part on determining that at least some electricalenergy cannot be routed to the battery 330 of the vehicle 300, the powersystem 350 can determine whether electrical energy can be routed to amotor 332 of the vehicle 300, as shown at operation 610. In at least oneexample, the power system 350 can determine whether the motor 332 iscapable of taking any of the electrical energy generated by the brakingforce(s). In some examples, the motor 332 may not be capable of takingthe electrical energy due to a limitation (e.g., a malfunction of acooling system, exceeding a maximum torque, etc.). Based at least inpart on determining that at least some electrical energy can be routedto the motor 332 of the vehicle 300, the power system 350 can route atleast some electrical energy to the motor 332, as shown at operation612. Based at least in part on determining that the motor 332 is capableof receiving at least some of the electrical energy generated, the powersystem 350 can route that electrical energy to the motor 332.

Based at least in part on determining that at least some electricalenergy cannot be routed to the motor 332 of the vehicle 300, the powersystem 350 can utilize at least some electrical energy (the electricalenergy that cannot be deposited in the motor 332) to affect force(s) onwheels(s) of the vehicle 300, as shown at operation 614. In at least oneexample, the power system 350 can utilize the electrical energy foraffecting a positive force on one or more wheels of the vehicle 300. Insuch an example, the power system 350 can utilize the electrical energyto apply a positive force to one or more wheel assemblies of the vehicle300. In some examples, the positive force can be equal to the negativebraking force applied by the power system 350 (e.g., if the battery 330and the motor 332 are not capable of taking any electrical energy and/orassuming no loss of energy via energy transfer). In other examples, thepositive force can be less than the negative braking force applied bythe power system 350 (e.g., if the battery 330 and/or the motor 332 arecapable of taking at least some electrical energy and/or assuming noloss of energy via energy transfer). In at least one example, themagnitude of the force(s) affected on the wheel(s) of the vehicle 300can be optimized based on friction circle(s) associated with thewheel(s), as described above.

The methods 400-600 are illustrated as collections of blocks in logicalflow graphs, which represent sequences of operations that can beimplemented in hardware, software, or a combination thereof. In thecontext of software, the blocks represent computer-executableinstructions stored on one or more computer-readable storage media that,when executed by one or more processors, perform the recited operations.Generally, computer-executable instructions include routines, programs,objects, components, data structures, and the like that performparticular functions or implement particular abstract data types. Theorder in which the operations are described is not intended to beconstrued as a limitation, and any number of the described blocks can becombined in any order and/or in parallel to implement the processes. Insome embodiments, one or more blocks of the process can be omittedentirely. Moreover, the methods 400-600 can be combined in whole or inpart with each other or with other methods.

The various techniques described herein can be implemented in thecontext of computer-executable instructions or software, such as programmodules, that are stored in computer-readable storage and executed bythe processor(s) of one or more computers or other devices such as thoseillustrated in the figures. Generally, program modules include routines,programs, objects, components, data structures, etc., and defineoperating logic for performing particular tasks or implement particularabstract data types.

Other architectures can be used to implement the describedfunctionality, and are intended to be within the scope of thisdisclosure. Furthermore, although specific distributions ofresponsibilities are defined above for purposes of discussion, thevarious functions and responsibilities might be distributed and dividedin different ways, depending on circumstances.

Similarly, software can be stored and distributed in various ways andusing different means, and the particular software storage and executionconfigurations described above can be varied in many different ways.Thus, software implementing the techniques described above can bedistributed on various types of computer-readable media, not limited tothe forms of memory that are specifically described.

EXAMPLE CLAUSES

A. A vehicle operable to travel in at least a first direction, thevehicle comprising: two or more wheel assemblies; a power systemoperable to provide power to enable the vehicle to accelerate; a brakesystem operable to cause, responsive to a braking action, a firstnegative force to be distributed between the two or more wheelassemblies to cause the vehicle to decelerate; and a control systemincluding: one or more processors; and one or more instructionsexecutable by the one or more processors to send a command, responsiveto the braking action, to at least one of the power system or the brakesystem to: cause the power system to affect a second negative force on afirst wheel assembly of the two or more wheel assemblies at a firsttime; and cause the power system to affect a positive force on a secondwheel assembly of the two or more wheel assemblies at a second time thatis substantially a same time as the first time, wherein an applicationof the second negative force and the positive force generates a brakeforce distribution such that a first total amount of braking forceapplied at the first wheel assembly is greater than a second totalamount of braking force applied at the second wheel assembly.

B. The vehicle paragraph A recites, wherein the first wheel assembly isa front wheel assembly and the second wheel assembly is a rear wheelassembly, relative to the first direction of travel, and the front wheelassembly is associated with an opposite end of the vehicle than the rearwheel assembly.

C. The vehicle as either paragraph A or B recites, wherein the powersystem is further operable to, responsive to the braking action, convertkinetic energy associated with a motion of the vehicle into electricalenergy and generate the positive force using at least a first portion ofthe electrical energy.

D. The vehicle as paragraph C recites, wherein the power system isfurther operable to: determine a state of a battery associated with thepower system; and route, based at least in part on the state of thebattery, a second portion of the electrical energy into the battery.

E. The vehicle as any of paragraphs A-D recite, wherein the one or moreinstructions are executable by the one or more processors further to:determine that a first friction coefficient associated with a firstwheel of the first wheel assembly differs from a second frictioncoefficient associated with a second wheel of the second wheel assembly;and send the command responsive to determining that the first frictioncoefficient differs from the second friction coefficient.

F. The vehicle as any of paragraphs A-E recite, wherein a firstmagnitude of the second negative force is substantially equal to asecond magnitude of the positive force.

G. The vehicle as any of paragraphs A-F recite, wherein the one or moreinstructions are executable by the one or more processors further to:determine a friction circle associated with the first wheel assembly,the friction circle defining a maximum magnitude of negative force basedat least in part on a direction of travel of the vehicle; anddetermining a magnitude of the second negative force based at least inpart on the maximum magnitude of negative force.

H. The vehicle as any of paragraphs A-G recite, wherein the first wheelassembly and the second wheel assembly have substantially symmetrichardware.

I. A computer-implemented method performed by one or more systems of avehicle, the computer-implemented method comprising: responsive to abraking action, causing, by a brake system of the one or more systems, afirst negative force to be distributed across at least two wheelassemblies of a vehicle; and sending a command to a power system of theone or more systems, the command instructing the power system to: affecta second negative force on a first wheel assembly of the at least twowheel assemblies so that a first total amount of braking force appliedat the first wheel assembly corresponds to a first sum of a firstportion of the first negative force and the second negative force; andaffect a positive force on a second wheel assembly of the at least twowheel assemblies so that a second total amount of braking force appliedat the second wheel assembly corresponds to a second sum of a secondportion of the first negative force and the positive force, the positiveforce being applied in a same direction as the vehicle is travelling.

J. The computer-implemented method as paragraph I recites, wherein thefirst wheel assembly is a front wheel assembly and the second wheelassembly is a rear wheel assembly, relative to a direction in which thevehicle is travelling, and the front wheel assembly is associated withan opposite end of the vehicle than the rear wheel assembly.

K. The computer-implemented method as paragraph I or J recites, furthercomprising: determining a friction circle associated with the firstwheel assembly; and determining a first magnitude of the second negativeforce and a second magnitude of the positive force based at least inpart on the friction circle associated with the first wheel assembly.

L. The computer-implemented method as any of paragraphs I-K recite,wherein a first magnitude of the second negative force and a secondmagnitude of the positive force are equal.

M. The computer-implemented method as any of paragraphs I-L recite,wherein a first magnitude of the second negative force and a secondmagnitude of the positive force are unequal.

N. The computer-implemented method as any of paragraphs I-M recite,wherein affecting the second negative force includes converting at leasta portion of kinetic energy associated with motion of the vehicle intoelectrical energy.

O. The computer-implemented method as paragraph N recites, furthercomprising: determining a state of a battery coupled to the powersystem; determining, based at least in part on the state of the battery,at least a portion of the electrical energy to utilize for the positiveforce; and utilizing at least the portion of the electrical energy toaffect the positive force.

P. A non-transitory computer-readable medium having a set ofinstructions that, when executed, cause one or more processors toperform operations comprising, during a period of deceleration, sendinga command to at least a power system of a vehicle to cause the powersystem to affect a negative force on a first wheel assembly of thevehicle and a positive force on a second wheel assembly of the vehicleto cause an uneven distribution of brake force between the first wheelassembly and the second wheel assembly.

Q. The non-transitory computer-readable medium as paragraph P recites,the operations further comprising sending the command responsive to anoccurrence of an event, wherein the event comprises at least one of: areceipt of a braking signal; a failure of a stability control system; ora difference between a first friction coefficient associated with afirst surface on which the first wheel assembly is located and a secondfriction coefficient associated with a second surface on which thesecond wheel assembly is located meets or exceeds a threshold.

R. The non-transitory computer-readable medium paragraph P or Q recites,wherein the first wheel assembly is a front wheel assembly and thesecond wheel assembly is a rear wheel assembly, relative to a directionin which the vehicle is travelling, and the front wheel assembly is onan opposite end of the vehicle than the rear wheel assembly.

S. The non-transitory computer-readable medium as any of paragraphs P-Rrecite, wherein the magnitude of the second negative force is greaterthan or equal to the magnitude of the positive force.

T. The non-transitory computer-readable medium as any of paragraphs P-Srecite, the operations further comprising: determining a state of acomponent of the power system that is configured to receive electricalenergy; and determining a magnitude of the positive force based at leastin part on the state of the component.

While paragraphs A-H are described above with respect to a system, it isunderstood in the context of this document that the content ofparagraphs A-H may also be implemented via a method, device, and/orcomputer storage media. While paragraphs I-O are described above withrespect to a method, it is understood in the context of this documentthat the content of paragraphs I-O may also be implemented via a system,device, and/or computer storage media. While paragraphs P-T aredescribed above with respect to a non-transitory computer-readablemedium, it is understood in the context of this document that thecontent of paragraphs P-T may also be implemented via a method, device,and/or system.

CONCLUSION

While one or more examples of the techniques described herein have beendescribed, various alterations, additions, permutations and equivalentsthereof are included within the scope of the techniques describedherein.

In the description of examples, reference is made to the accompanyingdrawings that form a part hereof, which show by way of illustrationspecific examples of the claimed subject matter. It is to be understoodthat other examples can be used and that changes or alterations, such asstructural changes, can be made. Such examples, changes or alterationsare not necessarily departures from the scope with respect to theintended claimed subject matter. While the steps herein can be presentedin a certain order, in some cases the ordering can be changed so thatcertain inputs are provided at different times or in a different orderwithout changing the function of the systems and methods described. Thedisclosed procedures could also be executed in different orders.Additionally, various computations that are herein need not be performedin the order disclosed, and other examples using alternative orderingsof the computations could be readily implemented. In addition to beingreordered, the computations could also be decomposed intosub-computations with the same results.

What is claimed is:
 1. A computer-implemented method comprising:causing, by a brake system of a vehicle, a first force to be applied toa first wheel of the vehicle and a second force to be applied to asecond wheel of the vehicle, wherein the first force and the secondforce are applied in a first direction that is opposite a seconddirection in which the vehicle is travelling; and sending, by a controlsystem of the vehicle, a command instructing a power system of thevehicle to affect a third force on the first wheel, wherein the thirdforce is applied in the second direction.
 2. The computer-implementedmethod of claim 1, wherein the command further instructs the powersystem to affect a fourth force on the second wheel, wherein the fourthforce is applied in the first direction.
 3. The computer-implementedmethod of claim 2, wherein a magnitude of the fourth force is based atleast in part on one or more of the first force, the second force, thethird force, or a weight of the vehicle.
 4. The computer-implementedmethod of claim 1, wherein the first force and the second force areapplied responsive to a braking action and the command is sentresponsive to the braking action, and wherein the first force and thesecond force have substantially similar magnitudes.
 5. Thecomputer-implemented method of claim 4, wherein the power system isfurther operable to, responsive to the braking action, convert kineticenergy associated with a motion of the vehicle into electrical energyand generate the third force using at least a first portion of theelectrical energy.
 6. The computer-implemented method of claim 5,further comprising: determining a state of a battery associated with thepower system; and routing, based at least in part on the state of thebattery, a second portion of the electrical energy into the battery. 7.The computer-implemented method of claim 1, further comprising:determining that a first friction coefficient associated with the firstwheel differs from a second friction coefficient associated with thesecond wheel; and sending the command responsive to determining that thefirst friction coefficient differs from the second friction coefficient.8. A system comprising: one or more processors; and one or moreinstructions executable by the one or more processors to performoperations comprising: causing, by a brake system of a vehicle, a firstforce to be applied to a first wheel of the vehicle and a second forceto be applied to a second wheel of the vehicle, wherein the first forceand the second force are applied in a first direction that is opposite asecond direction in which the vehicle is travelling; and sending, by acontrol system of the vehicle, a command instructing a power system ofthe vehicle to affect a third force on the first wheel, wherein thethird force is applied in the second direction.
 9. The system of claim8, wherein the command further instructs the power system to affect afourth force on the second wheel, wherein the fourth force is applied inthe first direction.
 10. The system of claim 9, the operations furthercomprising: determining a maximum magnitude of force that can be appliedin the first direction based at least in part on the second direction inwhich the vehicle is travelling; and determining a magnitude of thethird force and a magnitude of the fourth force based at least in parton the maximum magnitude of force that can be applied in the firstdirection.
 11. The system of claim 8, wherein the first force and thesecond force have substantially similar magnitudes, and wherein thefirst force and the second force are applied responsive to a brakingaction and the command is sent responsive to the braking action.
 12. Thesystem of claim 11, wherein the power system is further operable to,responsive to the braking action, convert kinetic energy associated witha motion of the vehicle into electrical energy and generate the thirdforce using at least a first portion of the electrical energy.
 13. Thesystem of claim 12, the operations further comprising: determining astate of a battery associated with the power system; and routing, basedat least in part on the state of the battery, a second portion of theelectrical energy into the battery.
 14. The system of claim 8, theoperations further comprising: determining that a first frictioncoefficient associated with the first wheel differs from a secondfriction coefficient associated with the second wheel; and sending thecommand responsive to determining that the first friction coefficientdiffers from the second friction coefficient.
 15. A non-transitorycomputer-readable medium having a set of instructions that, whenexecuted, cause one or more processors to perform operations comprising:causing, by a brake system of a vehicle, a first force to be applied toa first wheel of the vehicle and a second force to be applied to asecond wheel of the vehicle, wherein the first force and the secondforce are applied in a first direction that is opposite a seconddirection in which the vehicle is travelling; and sending a commandinstructing a power system to affect a third force on the first wheel,wherein the third force is applied in the second direction.
 16. Thenon-transitory computer-readable medium of claim 15, wherein the commandfurther instructs the power system to affect a fourth force on thesecond wheel, wherein the fourth force is applied in the firstdirection.
 17. The non-transitory computer-readable medium of claim 16,wherein the fourth force is based at least in part on one or more of thefirst force, the second force, the third force, or a weight of thevehicle.
 18. The non-transitory computer-readable medium of claim 15,wherein: the first force and the second force have a substantially equalmagnitude; the first force and the second force are applied responsiveto a braking action and the command is sent responsive to the brakingaction; and the power system is further operable to, responsive to thebraking action, convert kinetic energy associated with a motion of thevehicle into electrical energy and generate the third force using atleast a first portion of the electrical energy.
 19. The non-transitorycomputer-readable medium of claim 18, further comprising: determining astate of a battery associated with the power system; and routing, basedat least in part on the state of the battery, a second portion of theelectrical energy into the battery.
 20. The non-transitorycomputer-readable medium of claim 15, further comprising: determiningthat a first friction coefficient associated with the first wheeldiffers from a second friction coefficient associated with the secondwheel; and sending the command responsive to determining that the firstfriction coefficient differs from the second friction coefficient.